Bumpers are mounted at the forward extremity of a vehicle to protect the chassis of the vehicle from minor impacts. The bumper is mounted to the lower frame rails of the vehicle chassis for support thereof and functions to withstand minor impacts by collapsing to absorb the energy encountered through the impact.
The structure of a bumper can be formed in a “B-shaped” configuration with a front face flange and upper and lower cells. This B-shaped structural configuration can be seen in U.S. Pat. No. 6,042,163, issued to Raymond Reiffer on Mar. 28, 2000. The Reiffer patent discloses a bumper having a primary central member shaped in the “B” configuration with end pieces welded to the primary central member after formation to provide the ability to mount the bumper to the frame rails. A similar cross-sectional configuration is found in U.S. Pat. No. 6,684,505, issued on Feb. 3, 2004, to Anders Sundgren, et al. The Sundgren bumper is formed through a roll forming process from a uniform piece of sheet metal to create a thicker cross-section in the central portion than on the ends to facilitate the attachment of the bumper to the frame rails.
U.S. Patent Application Publication No. 2002/0053805, filed by Kazunari Azuchi, et al and published on May 9, 2002, is also directed to a B-shaped bumper configuration that absorbs impact through deformation of the upper and lower cells. The Azuchi bumper is formed with a central reinforcement section and connection sections at the terminal ends for connecting to the lower frame rails. The hollow central section includes a groove of varying depths to define the “B” configuration; however, the shape of the cross-section does not remain uniform along the length of the bumper. In fact, the groove separating the upper and lower cells of the B-shaped cross-section is reversed at the terminal ends in one embodiment to position the groove forwardly instead of rearwardly as formed in the central section.
Not all bumpers are formed in the B-shaped structural configuration, as is depicted in U.S. Pat. No. 5,997,058, issued to Roald Pedersen on Dec. 7, 1999. The Pedersen bumper is formed as a single cell hollow tube that has varying cross-section shapes along the longitudinal length of the bumper. The cross-sectional shape changes to provide a desired resilient effect for the bumper and to provide different energy absorption qualities along the longitudinal length of the bumper.
For conventional bumpers, enhancements to the cross-sectional configuration in the form of reinforcement inserts provide higher energy absorption qualities for those reinforced areas of the bumper, thus obtaining the desired variations in the collapsing of the bumper structure. Such reinforcements are conventionally placed at the attachment points between the bumper structure and the lower frame rails to allow for a greater absorption and dispersion of impact energy by the bumper before being transferred to the lower frame rail into the vehicle chassis.
Because, as will be described in greater detail below, the bumper incorporating the principles of the instant invention utilizes a tailor welded blank in the formation of the bumper configuration, U.S. Pat. No. 6,513,860, issued to Amar Ourchane, et al on Feb. 4, 2003, and owed by the Assignee of the instant application, is cited as a general teaching of an automotive component formed from a tailor welded blank in which portions of the sheet metal blank are initially formed with different material thicknesses and laser welded together to form a single blank from which the component is then formed, resulting in different thickness gages at different parts of the component.
It would be desirable to provide a lightweight bumper configuration that would be capable of crash performance characteristics of heavier conventional bumpers that are formed with reinforcement inserts. Designing the shape of the cells in the B-shaped cross-sectional configuration of the bumper to collapse in a prescribed manner can enhance crash performance and provide equivalent energy management of a significantly heavier conventional bumper.